JPS583819B2 - Hatsupousei Net Yuku Tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides a foaming heat-shrinkable material that easily shrinks and foams when heated, which can form a polymeric foam with good adhesion and good appearance on the surface of objects to be coated, such as pipes and rods. Regarding tubes.

In recent years, various products have been used for purposes such as insulation and heat retention, which are made by coating the outer periphery of pipes with polymeric foam. Covered pipes and other products have been well received.

Conventionally, this type of coating method has been put to practical use by extruding a polymer foam layer of a required thickness around the outer periphery of a metal pipe using an extrusion molding machine, or by using a polymer foam molded product that has been foamed and molded in advance. One method is to fit it into a metal pipe.

However, all of these methods require separate dies and molds for a wide variety of metal pipes with complex shapes and different diameters, and are irrational.

The present invention does not have such drawbacks, that is, it does not require a large number of dies or molds depending on the shape of the object to be coated, and is coated on the object to be coated and easily shrinks by heating. It is also an object of the present invention to provide a foamable heat-shrinkable tube that can be foamed to form a polymeric foam with excellent adhesion and appearance.

That is, the present invention provides a foamable tube obtained by extrusion molding a thermoplastic polymer blended and kneaded with a blowing agent, which is heated and softened, and the inside of the tube is pressurized or the outside of the tube is depressurized. This relates to a foamable heat-shrinkable tube whose diameter is increased by using the above method in combination.

To obtain the foamable heat-shrinkable tube of the present invention, first, a foamable tube is made.

The foamable tube mentioned here has an inner diameter smaller than the outer diameter of the object to be coated, and its wall thickness is usually about 0.1 to 1.
Refers to a tubular polymer molded product having a relatively flexible flexibility of about 1.0 mm, which foams to become a polymer foam when heated above the decomposition temperature of the foaming agent.

Therefore, this type of tube is made by blending a thermoplastic polymer with a blowing agent and, if necessary, various additives such as blowing aids, fillers, colorants, anti-aging agents, and stabilizers, using a mixing roll or an extruder. After kneading and pelletizing with a pelletizer, it can be obtained by extrusion molding with an extruder under conditions where the blowing agent is not decomposed at all or hardly.

Thermoplastic polymers used to manufacture the above-mentioned expandable tubes include polyethylene, ethylene-vinyl acetate copolymer, polypropylene, polystyrene, polyvinyl chloride, ethylene-propylene terpolymer, nitrile rubber, butyl rubber, acrylonitrile-butadiene-styrene rubber, etc. can be mentioned.

Blowing agents that should still be incorporated into these thermoplastic polymers include azo compounds such as azodicarbonamide, azobisimptilonitrile, nitroso compounds such as dinitrosopentamethylenetetramine, paratoluenesulfonylhydrazide, 4.4' - Select sulfonyl hydrazide compounds such as oxybisbenzenesulfonyl hydrazide, whose decomposition temperature is higher than the softening point of the thermoplastic polymer, and which does not decompose at all or hardly during extrusion molding. and use it.

Representative examples of foaming aids that can be used in combination with the foaming agent include urea, metal salts of carboxylic acids, and the like.

The amount of foaming agent and foaming aid used must be determined appropriately depending on the type of foaming heat shrinkable tube so that a predetermined expansion ratio can be obtained when the foamable heat-shrinkable tube is foamed.Usually, the total amount mentioned above is the amount of the thermoplastic polymer. The amount may be 1 to 20 parts by weight per 100 parts by weight.

Specific examples of various additives that may be added as necessary include:
Talc, clay, silica, alumina, barium sulfate, metal powder, glass beads, short glass fibers, etc. are used as fillers, and titanium oxide, carbon, phthalocyanine, etc. are used as coloring agents. Blue, Mapico Yellow (manufactured by Titan Kogyo Co., Ltd.,
Pigments and dyes such as Shinkasha Red (trade name, manufactured by DuPont) are used as anti-aging agents and stabilizers. and amine compounds such as phenyl β-naphthylamine and phenyl α-naphthylamine.

The proportion of these additives to be used is such that the total amount thereof is usually about 0.1 to 3 parts by weight per 100 parts by weight of the thermoplastic polymer.

In the present invention, such a foamable tube is subjected to a crosslinking treatment if necessary.

Ionizing radiation irradiation such as electron beams and gamma rays or ultraviolet irradiation are particularly effective as crosslinking treatment methods, but
Other methods may also be used, such as mixing and kneading a crosslinking agent or a crosslinking accelerator with the crosslinking agent in advance during production of the expandable tube, and heating and crosslinking with these ingredients.

Examples of the crosslinking agent and crosslinking accelerator include peroxides such as dicumyl peroxide, lauryl peroxide, penzoyl peroxide, and methyl ethyl ketone peroxide, tetramethylthiuram disulfide,
Examples include thiuram compounds such as tetramethylthiuram monosulfide, dithiocarbamate compounds such as zinc dimethyldithiocarbamate and dithiocarbamate, and the total amount is usually about 0.2 to 4 parts by weight based on 100 parts by weight of the thermoplastic polymer. Use parts by weight.

In the case of thermal crosslinking, it is necessary to carry out the crosslinking at a temperature at which the blowing agent does not separate at all or hardly, and therefore, as the crosslinking agent and crosslinking accelerator, those satisfying the above requirements are selected and used.

By enlarging the diameter of the expandable tube, which will be described later, by the above-mentioned crosslinking treatment, the heat shrinkability imparted becomes greater.

In the present invention, the crosslinked foam tube is then enlarged until its inner diameter is larger than the outer diameter of the object to be coated.

This diameter enlargement is carried out while the foamable tube is heated and softened (above the softening temperature and below the melting temperature) by, for example, pressurizing the inside of the tube, reducing the pressure outside the tube, or using the above methods in combination.

As a method of pressurizing the inside of the tube, for example, as shown in FIG. 1, a foam tube 3 is attached to a pressurizing tube 2 having a pressurizing port 1, and the tube 3 is heated and softened by any means to form a pressurizing port. 1, a predetermined gas may be pressurized into the tube interior 4, thereby enlarging the diameter of the tube 3 to the inner wall surface 5 of the pressurizing tube 2, as shown in FIG.

On the other hand, a method for reducing the pressure on the outside of the tube will be explained with reference to FIG. 1. Air inside the gap 6 between the foam tube 3 and the pressurizing tube 2 is sucked from a predetermined position to reduce the pressure in the gap 6. state.

At this time, if the foamable tube 3 is heated and softened, the diameter can be increased as shown in FIG. 2 in the same manner as described above.

When softening a foamable tube by heating, it is necessary to heat the tube to a temperature below the decomposition temperature of the foaming agent so that the tube does not foam at all or hardly.

Such diameter enlarging treatment imparts excellent heat shrinkability to the foamable tube.

This heat shrinkability differs depending on the degree of diameter enlargement, and preferably, the inner diameter of the expandable tube manufactured by extrusion molding is made as small as possible than the outer diameter of the object to be coated, so that the degree of diameter enlargement is adjusted. It is best to make it twist a lot, and usually the inner diameter (or outer diameter) is made to be about 1.2 to 3 times larger.

Further, as described above, this heat shrinkability is further increased by performing crosslinking treatment prior to increasing the diameter.

The foamable heat-shrinkable tube of the present invention thus obtained has a wall thickness of about 0.1 to 1.5 mm and is flexible, and easily shrinks and foams when heated. The following method is used to actually coat the object to be coated.

That is, the covering object is first covered with a foamable heat-shrinkable tube, and then the tube is heated to a temperature equal to or higher than the softening point of the thermoplastic polymer to cause it to shrink and foam.

By this heating, the tube first shrinks and comes into close contact with the object to be coated.

Next, foaming is started in this close contact state, and a polymer foam having a predetermined foaming ratio with good adhesion and good appearance is formed on the surface of the object to be covered, and the object to be covered is covered with the foamed material. It will be covered with your body.

As detailed above, the foamable heat-shrinkable tube of the present invention is made by enlarging the diameter of a foamable tube obtained by extrusion molding by any means, and as long as the inner diameter of the tube is regulated, the tube can be coated. A desired polymeric foam layer can be formed on the surface of the object simply by coating it on an object, heating it, and foaming it.Moreover, the inner diameter of the tube can be easily regulated by increasing the diameter, and the tube itself can be heated and foamed.
Even if the above-mentioned inner diameter, which should be regulated in order to undergo heat shrinkage during foaming, is considerably larger than the outer diameter of the object to be coated, there is no problem and a particularly strict diameter size of C is not required, and therefore, this invention According to the method, the object to be coated can be coated much more advantageously than the conventional method which requires the use of various types of dies and molds depending on the shape of the object to be coated.

Moreover, the tube of the present invention is relatively flexible, and as described above, the inner diameter can be made much larger than the outer diameter of the object to be coated, so objects to be coated such as pipes and rods can be Of course, even various objects to be coated with complex shapes such as joints, elbows, flanges, etc. can be easily coated.
In addition, during heating and foaming after coating, the polymer foam to be formed can be firmly adhered to the surface of the object to be coated by utilizing the heat shrinkability of the tube itself and the expansion force due to foaming. Even if the outer diameter of the object to be coated is much larger than the outer diameter of the object to be coated, or even if the object is to be coated with a complicated shape, it is possible to create almost no voids at the interface between the object to be coated and the polymer foam formed. It is possible to form a polymer foam that always has good adhesion without causing any problems, and as a result has an excellent appearance.

When the tube of the present invention is used to coat the object with a polymeric foam of a predetermined expansion ratio, the foam provides various functions such as heat retention, insulation, cushioning, protection, and floating. It can be used for various purposes that make effective use of these functions.

Next, the present invention will be explained in more detail with reference to Examples.

In addition, in the following, parts indicate parts by weight.

Example 1 100 parts of polyethylene (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumikasen L-705, softening point: 86°C) and 8 parts of a blowing agent, manufactured by Eiwa Kasei Co., Ltd., trade name Pinihole DW#6) were mixed using a mixing roll. After kneading, pelletize with a pelletizer and use an extruder at a temperature 1 at which the blowing agent does not decompose.
A foam tube with a thickness of 450μ and an inner diameter of 20mm is made at 30°C.

Using an electron beam accelerator on this tube, 3Mev, 5mA was generated.
The tube is cross-linked by irradiation with an electron beam of 3 Mrad to cross-link the polyethylene.

Next, the foamed tube after the crosslinking treatment was placed in a pressure tube (length 1 m, inner diameter 35 mm) shown in Fig. 1, and was pressurized and heated in an atmosphere of 120°C for 5 minutes to a thickness of 350 μm and an outer diameter of 35 m.
A foamable heat-shrinkable tube of m was obtained.

This foamable heat-shrinkable tube is cut into a length of 30 cm, and a steel pipe having a length of 30 cm and an outer diameter of 25 mm is inserted into the tube to cover the steel pipe.

Thereafter, the tube was heated at 180° C. for 10 minutes to foam, resulting in the formation of a polymer foam that adhered well to the surface of the steel pipe and had an excellent appearance.

This foam has an expansion ratio of 9 times and has excellent heat insulation and cushioning properties.

Example 2 Ethylene vinyl acetate copolymer (manufactured by Mitsui Polychemical Co., Ltd., trade name: Everex P1907 Softening point: 59°C
) and 10 parts of a blowing agent (manufactured by Sankyo Kasei Co., Ltd., trade name: Cellmic CAP) were kneaded using a mixing roll, and then an extruder was used to mold the die at a die temperature of 110°C so that the blowing agent did not decompose, to a thickness of 500μ and an inner diameter. Make a 20mm foam tube.

Using an electron beam accelerator on this tube, 3Mev, 5mA
The tube is cross-linked by irradiation with an electron beam of 3 Mrad to cross-link the polyethylene.

Next, the foamed tube after the crosslinking treatment was placed in the pressure tube shown in Figure 1 (same as in Example 1), and heated and pressurized for 5 minutes in an atmosphere of 105°C to form a tube with a thickness of 400 μm and an outer diameter of 35 mm. A foamable heat-shrinkable tube was obtained.

Insert an aluminum tube with an outer diameter of 25 mm into this foamed heat shrink tube. The aluminum tube is covered with the tube.

The tube was then heated at 150° C. for 10 minutes to foam, resulting in the formation of a polymer foam that adhered well to the surface of the aluminum tube, had a foaming ratio of 8 times, and had excellent appearance, heat insulation, and elasticity. It was done.

Example 3 100 parts of polyethylene (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumikasen F-208-1, softening point = 95°C), blowing agent (manufactured by Eiwa Kasei Co., Ltd., trade name: Vinyhole AC#3)
) and 1 part of the crosslinking agent (dicumyl peroxide) were kneaded with a mixing roll, pelletized with a pelletizer, and then molded with an extruder at a temperature of 160 to 180°C at which the blowing agent does not decompose to a thickness of 700μ and an inner diameter of 30mm. Make a foam tube.

This tube was heated at 160°C for 10 minutes to carry out crosslinking treatment with the peroxide, and then installed in a pressure tube (length 1m, inner diameter 60mm) shown in Fig. 1.
Pressurized and heated for 10 minutes in an atmosphere of ℃ to a thickness of 470μ,
A foamable heat-shrinkable tube with an outer diameter of 60 mm was obtained.

Easily fit this foam heat shrink tube into the 45 degree elbow, cover the elbow with the tube, and then
When the tube was heated and foamed at 20° C. for 10 minutes, a polymer foam with excellent adhesion and appearance was formed.

It is very difficult to attach polymeric foam to such an elbow using the conventional method, and the above results demonstrate how excellent the foamable heat-shrinkable tube of the present invention is.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a device for enlarging the diameter of a foamable tube according to the present invention, and FIG. 2 is a sectional view of the same, showing the state when the diameter is enlarged. 3... Foaming tube.

Claims (1)

[Claims] 1. A foamable heat-shrinkable tube obtained by extruding a thermoplastic polymer blended and kneaded with a foaming agent and enlarging the diameter while softening the foamable tube.